scope:

The guideline VDI 3927 Part 1 [18] describes waste gas cleaning processes for the removal of gaseous air pollutants and aerosols like sulphur oxides and nitrogen oxides, and halides from flue gases generated by combustion processes.

This guideline VDI 3927 Part 2 deals with waste gas cleaning processes for the removal of inorganic and organic trace species. The information provided hereinafter applies primarily to flue gases from firing systems and can be applied to process plants to a limited extent only. Process-internal recycling plays a specific part in process plants. This is described in detail in the relevant VDI guidelines [19 through 23]. Individual technologies described in this Part 2 of VDI 3927, however, are also suitable for final treatment stages downstream of process plants, where such stages may be required as a consequence of particular site-specific provisions by the authorities.

In the case of particulate inorganic or organic trace species, reference is also made to the relevant guidelines on dust collectors [24 through 29]. In this context, particular consideration shall be given to the separation curve of the dust collectors for finergrained fractions.

As far as primary emission-control measures, i.e. emission-control measures to be taken on the combustion side, are concerned, reference is made to the detailed description in conjunction with thermal waste treatment [19]. In addition to describing process- dependent measures, the VDI guideline on emission control in the combustion of wood [20; 21] also refers, in general form, to possible flue gas cleaning processes to be detailed in this guideline. By contrast, the focus is laid on internal material recycling in plants for the production of cement [22] and glass [23]. The use of the process equipment described below is only convenient in exceptional cases, e.g. where additional site-specific provisions by the authorities have to be met.

Thermal and catalytic post-combustion processes, which, in principle, are also suitable for decomposing organic trace species, are not used specifically to serve this purpose, particularly not downstream of combustion systems. No investigations or experiences are available as to the composition of combustion flue gases. The available data refers exclusively to volatile organic compounds (VOC) in the waste gases from other types of plants [30; 31].

Also, this guideline does not cover the emissions produced by combustion engines.